Transmission rate control method and mobile station

ABSTRACT

A transmission rate control method for controlling a transmission rate of data transmitted from a mobile station to a radio base station via an uplink, includes: receiving, at the mobile station, an Absolute Rate Grant Channel which indicates an absolute value of the transmission rate from the radio base station; and ignoring, at the mobile station, a Relative Rate Grant Channel which indicates a relative value of the transmission rate until each HARQ process has been performed once, after receiving the Absolute Rate Grant Channel.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. P2005-134640, filed on May 2,2005; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transmission rate control method forcontrolling transmission rate in uplink, a mobile station, and a radiobase station.

2. Description of the Related Art

In a conventional mobile communication system, in an uplink from amobile station UE to a radio base station Node B, a radio networkcontroller RNC is configured to determine a transmission rate of adedicated channel, in consideration of radio resources of the radio basestation Node B, an interference volume in an uplink, transmission powerof the mobile station UE, transmission processing performance of themobile station UE, a transmission rate required for an upperapplication, and the like, and to notify the determined transmissionrate of the dedicated channel by a message of a layer-3 (Radio ResourceControl Layer) to both of the mobile station UE and the radio basestation Node B.

Here, the radio network controller RNC is provided at an upper level ofthe radio base station Node B, and is an apparatus configured to controlthe radio base station Node B and the mobile station UE.

In general, data communications often cause burst traffic compared withvoice communications or TV communications. Therefore, it is preferablethat a transmission rate of a channel used for the data communicationsis changed fast.

However, as shown in FIG. 1, the radio network controller RNC integrallycontrols a plurality of radio base stations Node B in general.Therefore, in the conventional mobile communication system, there hasbeen a problem that it is difficult to perform fast control for changingof the transmission rate of channel (for example, per approximately 1through 100 ms), due to processing load, processing delay, or the like.

In addition, in the conventional mobile communication system, there hasbeen also a problem that costs for implementing an apparatus and foroperating a network are substantially increased even if the fast controlfor changing of the transmission rate of the channel can be performed.

Therefore, in the conventional mobile communication system, control forchanging of the transmission rate of the channel is generally performedon the order from a few hundred ms to a few seconds.

Accordingly, in the conventional mobile communication system, when burstdata transmission is performed as shown in FIG. 2A, the data aretransmitted by accepting low-speed, high-delay, and low-transmissionefficiency as shown in FIG. 2B, or, as shown in FIG. 2C, by reservingradio resources for high-speed communications to accept that radiobandwidth resources in an unoccupied state and hardware resources in theradio base station Node B are wasted.

It should be noted that both of the above-described radio bandwidthresources and hardware resources are applied to the vertical radioresources in FIGS. 2B and 2C.

Therefore, the 3rd Generation Partnership Project (3GPP) and the 3rdGeneration Partnership Project 2 (3GPP2), which are internationalstandardization organizations of the third generation mobilecommunication system, have discussed a method for controlling radioresources at high speed in a layer-1 and a media access control (MAC)sub-layer (a layer-2) between the radio base station Node B and themobile station UE, so as to utilize the radio resources effectively.Such discussions or discussed functions will be hereinafter referred toas “Enhanced Uplink (EUL)”.

In the field of the Enhanced Uplink (EUL), as shown in FIG. 3, themobile station UE is configured to receive an “Absolute Rate GrantChannel (AGCH)” from a serving cell, and to receive a “Relative RateGrant Channel (RGCH)” from the serving cell and non-serving cells.

Whenever the mobile station UE receives the AGCH, the mobile station UEis configured to transmit an uplink data in a target TTI (TransmissionTime Interval) using the transmission rate (or a transmission poweroffset) which is indicated by the AGCH, irrespective of whether or notto receive of the RGCH.

On the other hand, as shown in FIG. 4, when the mobile station does notreceive the AGCH, and detects “UP” command or “DOWN” command in theRGCH, the mobile station UE is configured to increase/decrease thetransmission rate (the transmission power offset) in a previous TTIwhich belongs to the same HARQ process as the target TTI bypredetermined value, and to determine the transmission rate (thetransmission power offset) in the target TTI.

As shown in FIG. 5, the AGCH is used to increase the transmission rateinstantaneously, or the like.

However, when the mobile station UE erroneously detects the RGCH, so asto determine that “UP” command or “DOWN” command is received at themobile station UE against the instruction of the radio base station NodeB, and when the above mentioned method for determining the transmissionrate (transmission power ratio) is used, the transmission rate on theTTI prior to the TTI in which the transmission rate was changedinstantaneously by the AGCH is increased/decreased. Therefore, the fasttransmission rate control using the AGCH cannot be performed.

To be more specific, as shown in FIG. 6, the radio base station Node Btransmits the AGCH to the mobile station UE which is transmitting thedata at the transmission rate of 100 kbps in t=3 [TTI]. Then, thetransmission rate in uplink in the mobile station UE increase up to1Mbps in t=5 [TTI].

When the mobile station UE erroneously detects “UP” command in the RGCHin t=6 [TTI], the transmission rate is increased by the predeterminedvalue from the transmission rate in t=2 [TTI] which is the previous TTIbelongs to the same HARQ process as t=6 [TTI].

In other words, When the mobile station UE erroneously detects “UP”command in the RGCH in t=6 [TTI], the transmission rate is increased bythe predetermined value from the transmission rate of 100 kbps in t=2[TTI].

As a result, the transmission rate, which has been increased up to 1Mbpsby the AGCH, decreases rapidly. Therefore, there has been a problem thatcertain processing such as retransmitting of the AGCH needed to beperformed, and a transmission delay occurs.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made considering the problems, and itsobject is to provide a transmission rate control method, a mobilestation and a radio base station, which can achieve a smooth datatransmission by preventing a rapid decrease of a transmission rate whichis caused by erroneous detection of a Relative Rate Grant Channel.

A first aspect of the present invention is summarized as a transmissionrate control method for controlling a transmission rate of datatransmitted from a mobile station to a radio base station via an uplink,including: receiving, at the mobile station, an Absolute Rate GrantChannel which indicates an absolute value of the transmission rate fromthe radio base station; and ignoring, at the mobile station, a RelativeRate Grant Channel which indicates a relative value of the transmissionrate until each HARQ process has been performed once, after receivingthe Absolute Rate Grant Channel.

A second aspect of the present invention is summarized as a mobilestation for controlling a transmission rate of data transmitted to aradio base station via an uplink, including: a receiving sectionconfigured to receive an Absolute Rate Grant Channel which indicates anabsolute value of the transmission rate from the radio base station; anda controlling section configured to ignore a Relative Rate Grant Channelwhich indicates a relative value of the transmission rate until eachHARQ process has been performed once, after receiving the Absolute RateGrant Channel.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is diagram of an entire configuration of a general mobilecommunication system.

FIGS. 2A to 2C are graphs illustrating operations at the time of burstdata transmission in a conventional mobile communication system.

FIG. 3 is a diagram showing transmission rate control channelstransmitted in a conventional mobile communication system.

FIG. 4 is a diagram for explaining operations of the conventional mobilecommunication system.

FIG. 5 is a diagram for explaining operations of the conventional mobilecommunication system.

FIG. 6 is a diagram for explaining operations of the conventional mobilecommunication system.

FIG. 7 is a functional block diagram of a mobile station in the mobilecommunication system according to an embodiment of the presentinvention.

FIG. 8 is a functional block diagram of a baseband signal processingsection of the mobile station in the mobile communication systemaccording to the embodiment of the present invention.

FIG. 9 is a functional block diagram of a MAC-e processing section ofthe baseband signal processing section in the mobile station of themobile communication system according to the embodiment of the presentinvention.

FIG. 10 is a functional block diagram of a radio base station of themobile communication system according to the embodiment of the presentinvention.

FIG. 11 is a functional block diagram of a baseband processing sectionin the radio base station of the mobile communication system accordingto the embodiment of the present invention.

FIG. 12 is a functional block diagram of a MAC-e and layer-1 processingsection (configured for an uplink) in the baseband signal processingsection in the radio base station of the communication system accordingto the embodiment of the present invention.

FIG. 13 is a functional block diagram of the MAC-e functional section ofthe MAC-e and layer-1 processing section (configured for the uplink) inthe baseband signal processing section in the radio base station of themobile communication system according to the embodiment of the presentinvention.

FIG. 14 is a functional block diagram of a radio network controller ofthe mobile communication system according to the embodiment of thepresent invention.

FIG. 15 is a flowchart showing operations of the mobile communicationsystem according to the embodiment of the present invention.

FIG. 16 is a diagram for explaining operations of the mobilecommunication system according to the embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

(Configuration of Mobile Communication System According to FirstEmbodiment of the Present Invention)

Referring to FIGS. 7 to 14, a configuration of a mobile communicationsystem according to a first embodiment of the present invention will bedescribed.

It should be noted that, as shown in FIG. 1, the mobile communicationsystem according to this embodiment is provided with a plurality ofradio base stations Node B #1 to Node B #5 and a radio networkcontroller RNC.

The mobile communication system according to this embodiment, a “HighSpeed Downlink Packet Access (HSDPA)” is used in a downlink, and an“Enhanced Uplink (EUL)” is used in an uplink.

It should be noted that in both of the HSDPA and the EUL, retransmissioncontrol (N process stop and wait) shall be performed by a “HybridAutomatic Repeat Request (HARQ)”.

Therefore, in an uplink, an “Enhanced Dedicated Physical Channel(E-DPCH)” configured of an “Enhanced Dedicated Physical Data Channel(E-DPDCH)” and an “Enhanced Dedicated Physical Control Channel(E-DPCCH)”, and a “Dedicated Physical Channel (DPCH)” configured of a“Dedicated Physical Date Channel (DPDCH)” and a “Dedicated PhysicalControl Channel (DPCCH)” are used.

Here, the E-DPCCH transmits control data for the EUL such as atransmission format number for defining a transmission format(transmission block size, or the like) of the EDPDCH, HARQ relatedinformation (the number of retransmission, or the like), and schedulingrelated information (transmission power, buffer residence-volume, or thelike in the mobile station UE).

In addition, the E-DPDCH is paired with the E-DPCCH, and transmits userdata for the mobile station UE based on the control data for the EULtransmitted through the E-DPCCH.

The DPCCH transmits control data such as a pilot symbol that is used forRAKE combining, SIR measurement, or the like, a Transport FormatCombination Indicator (TFCI) for identifying a transmission format ofuplink DPDCH, and a transmission power control bit in a downlink.

In addition, the DPDCH is paired with the DPCCH, and transmits user datafor the mobile station UE based on the control data transmitted throughthe DPCCH. However, if user data that should be transmitted does notexist in the mobile station UE, the DPDCH can be configured not to betransmitted.

In addition, in the uplink, a “High Speed Dedicated Physical ControlChannel (HS-DPCCH)” which are needed when the HSPDA is applied, and a“Random Access Channel (RACH)”, are also used.

The HS-DPCCH transmits a Channel Quality Indicator (CQI) in a downlinkand an acknowledge signal (Ack or Nack) for the HS-DPCCH.

As shown in FIG. 7, the mobile station UE according to this embodimentis provided with a bus interface 31, a call processing section 32, abaseband processing section 33, a radio frequency (RF) section 34, and atransmission-reception antenna 35.

However, these functions can be independently present as hardware, andcan be partly or entirely integrated, or can be configured through aprocess of software.

The bus interface 31 is configured to forward the user data output fromthe call processing section 32 to another functional section (forexample, an application related functional section). In addition, thebus interface 31 is configured to forward the user data transmitted fromanother functional section (for example, the application relatedfunctional section) to the call processing section 32.

The call processing section 32 is configured to perform a call controlprocessing for transmitting and receiving the user data.

The baseband signal processing section 33 is configured to transmit theuser data to the call processing section 32, the user data acquired byperforming, against the baseband signals transmitted from the RF section34, a layer-1 processing including a despreading processing, a RAKEcombining processing, and a “Forward Error Correction (FEC)” decodeprocessing, a “Media Access Control (MAC)” processing including a MAC-eprocessing and a MAC-d processing, and a “Radio Link Control (RLC)”processing.

In addition, the baseband signal processing section 33 is configured togenerate the baseband signals by performing the RLC processing, the MACprocessing, or the layer-1 processing against the user data transmittedfrom the call processing section 32 so as to transmit the basebandsignals to the RF section 34.

Detailed description of the functions of the baseband signal processingsection 33 will be given later.

The RF section 34 is configured to generate baseband signals byperforming the detection processing, the filtering processing, thequantization processing, or the like against radio frequency signalsreceived through the transmission-reception antenna 35, so as totransmit the generated baseband signals to the baseband signalprocessing section 33.

In addition, the RF section 34 is configured to convert the basebandsignals transmitted from the baseband signal processing section 33 tothe radio frequency signals.

As shown in FIG. 8, the baseband signal processing section 33 isprovided with a RLC processing section 33 a, a MAC-d processing section33 b, a MAC-e processing section 33 c, and a layer-1 processing section33 d.

The RLC processing section 33 a is configured to transmit, to the MAC-dprocessing section 33 b, the user data transmitted from the callprocessing section 32 by performing a processing (RLC processing) in anupper layer of a layer-2 against the user data.

The MAC-d processing section 33 b is configured to grant a channelidentifier header, and to create a transmission format in the uplinkbased on the limitation of transmission power.

As shown in FIG. 9, the MAC-e processing section 33 c is provided withan Enhanced Transport Format Combination (E-TFC) selecting section 33 c1 and an HARQ processing section 33 c 2.

The E-TFC selecting section 33 c 1 is configured to determine atransmission format (E-TFC) of the E-DPDCH and the E-DPCCH, based onscheduling signals transmitted from the radio base station Node B.

In addition, the E-TFC selecting section 33 c 1 is configured totransmit transmission format information on the determined transmissionformat (that is, a transmission data block size, an transmission powerratio between the E-DPDCH and the DPCCH, or the like) to the layer-1processing section 33 d, and also to transmit the determinedtransmission format information to the HARQ processing section 33 c 2.

Such a scheduling signal is information that is signaled in the cellwhere the mobile station UE is located, and includes control informationfor all the mobile stations located in the cell, or a specific group ofthe mobile stations located in the cell.

The HARQ processing section 33 c 2 is configured to perform processcontrol for the “N-process stop-and-wait”, so as to transmit the userdata in the uplink based on an acknowledge signal (Ack/Nack for uplinkdata) transmitted from the radio base station Node B.

Specifically, the HARQ 33 c 2 is configured to determine whether or notthe receive processing of downlink user data has been successful basedon the result of the “Cyclic Redundancy Check (CRC)” entered from thefirst layer processing section 33 d.

Then, the HARQ processing section 33 c 2 is configured to generate anacknowledge signal (Ack/Nack for downlink user data) based on thedetermined result, so as to transmit the acknowledge signal to thelayer-1 processing section 33 d.

In addition, the HARQ processing section 33 c 2 is configured totransmit, to the MAC-d processing 33 b, the downlink user data enteredfrom the layer-1 processing section 33 d when the above-describeddetermination result has been successful.

As shown in FIG. 10, the radio base station Node B according to thisembodiment is provided with an HWY interface 11, a baseband signalprocessing section 12, a call control section 13, at least onetransmitter-receiver section 14, at least one amplifier section 15, andat least one transmission-reception antenna 16.

The HWY interface 11 is an interface with a radio network controllerRNC. Specifically, the HWY interface 11 is configured to receive userdata transmitted from the radio network controller RNC to a mobilestation UE via a downlink, so as to enter the user data to the basebandsignal processing section 12.

In addition, the HWY interface 11 is configured to receive control datafor the radio base station Node B from the radio network controller RNC,so as to enter the received control data to the call control section 13.

In addition, the HWY interface 11 is configured to acquire, from thebaseband signal processing section 12, the user data included in theuplink signals which are received from a mobile station UE via anuplink, so as to transmit the acquired user data to the radio networkcontroller RNC.

Further, the HWY interface 11 is configured to acquire the control datafor the radio network controller RNC from the call control section 13,so as to transmit the acquired control data to the radio networkcontroller RNC.

The baseband signal processing section 12 is configured to generatebaseband signals by performing the RLC processing, the MAC processing(the MAC-d processing and the MAC-e processing), or the layer-1processing against the user data acquired from the HWY interface 11, soas to forward the generated baseband signals to the transmitter-receiversection 14.

Here, the MAC processing in the downlink includes an HARQ processing, ascheduling processing, a transmission rate control processing, or thelike.

In addition, the layer-1 processing in the downlink includes a channelcoding processing of user data, a spreading processing, or the like.

In addition, the baseband signal processing section 12 is configured toextract user data by performing the layer-1 processing, the MACprocessing (the MAC-e processing and the MAC-d processing), or the RLCprocessing against the baseband signals acquired from thetransmitter-receiver section 14, so as to forward the extracted userdata to the HWY interface 11.

Here, the MAC-e processing in the uplink includes the HARQ processing,the scheduling processing, the transmission rate control processing, aheader disposal processing, or the like.

In addition, the layer-1 processing in the uplink includes thedespreading processing, the RAKE combining processing, the errorcorrection decode processing, or the like.

Detailed description of the functions of the baseband signal processingsection 12 will be given later.

In addition, the call control section 13 is configured to perform callcontrol processing based on the control data acquired from the HWYinterface 11.

The transmitter-receiver section 14 is configured to perform processingof converting baseband signals, which are acquired from the basebandsignal processing section 12, to radio frequency signals (downlinksignals), so as to transmit the radio frequency signals to the amplifiersection 15.

In addition, the transmitter-receiver 14 is configured to performprocessing of converting the radio frequency signals (uplink signals),which are acquired from the amplifier section 15, to the basebandsignals, so as to transmit the baseband signals to the baseband signalprocessing section 12.

The amplifier section 15 is configured to amplify the downlink signalsacquired from the transmitter-receiver section 14, so as to transmit theamplified downlink signals to the mobile station UE via thetransmission-reception antenna 16.

In addition, the amplifier 15 is configured to amplify the uplinksignals received by the transmission-reception antenna 16, so as totransmit the amplified uplink signals to the transmitter-receiversection 14.

As shown in FIG. 11, the baseband signal processing section 12 isprovided with a RLC processing section 121, a MAC-d processing section122, and a MAC-e and first layer processing section 123.

The MAC-e and layer-1 processing section 123 is configured to perform,against the baseband signals acquired from the transmitter-receiversection 14, the despreading processing, the RAKE combining processing,the error correction decode processing, the HARQ processing, or thelike.

The MAC-d processing section 122 is configured to perform a headerdisposal processing against output signals from the MAC-e and layer-1processing section 123.

The RLC processing section 121 is configured to perform, against theoutput signals from the MAC-d processing section 122, the retransmissioncontrol processing in the RLC layer or the reestablishment processing ofRLC-Service Data Section (SDU).

However, these functions are not clearly divided per hardware, and canbe obtained by software.

As shown in FIG. 12, the MAC-e and layer-1 processing section(configuration for the uplink) 123 is provided with a DPCCH RAKE section123 a, a DPDCH RAKE section 123 b, an E-DPCCH RAKE section 123 c, anE-DPDCH RAKE section 123 d, an HS-DPCCH RAKE section 123 e, a RACHprocessing section 123 f, a Transport Format Combination Indicator(TFCI) decoder section 123 g, buffers 123 h and 123 m, re-despreadingsections 123 i and 123 n, FEC decoder sections 123 j and 123 p, anE-DPCCH decoder section 123 k, a MAC-e functional section 123 l, an HARQbuffer 123 o, and a MAC-hs functional section 123 q.

The E-DPCCH RAKE section 123 c is configured to perform, against theE-DPCCH in the baseband signals transmitted from thetransmitter-receiver section 14, the despreading processing and the RAKEcombining processing using a pilot symbol included in the DPCCH.

The E-DPCCH decoder section 123 k is configured to acquire transmissionformat number related information, HARQ related information, schedulingrelated information, or the like, by performing the decode processingagainst the RAKE combining outputs of the E-DPCCH RAKE section 123 c, soas to enter the information to the MAC-e functional section 123 l.

The E-DPDCH RAKE section 123 d is configured to perform, against theE-DPDCH in the baseband signals transmitted from thetransmitter-receiver section 14, the despreading processing using thetransmission format information (the number of codes) transmitted fromthe MAC-e functional section 123 l and the RAKE combining processingusing the pilot symbol included in the DPCCH.

The buffer 123 m is configured to store the RAKE combining outputs ofthe E-DPDCH RAKE section 123 d based on the transmission formatinformation (the number of symbols) transmitted from the MAC-efunctional section 123 l.

The re-despreading section 123 n is configured to perform thedespreading processing against the RAKE combining outputs of the E-DPDCHRAKE section 123 d stored in the buffer 123 m, based on the transmissionformat information (spreading factor) transmitted from the MAC-efunctional section 123 l.

The HARQ buffer 123 o is configured to store the despreading processingoutputs of the re-despreading section 123 n, based on the transmissionformat information transmitted from the MAC-e functional section 123 l.

The FEC decoder section 123 p is configured to perform an errorcorrection decoding processing (the FEC decode processing) against thedespreading processing outputs of the re-despreading section 123 n,which is stored in the HARQ buffer 123 o, based on the transmissionformat information (transmission data block size) transmitted from theMAC-e functional section 123 l.

The MAC-e functional section 123 l is configured to calculate and outputthe transmission format information (the number of codes, the number ofsymbols, spreading factor, transmission data block size, and the like)based on the transmission format number related information, the HARQrelated information, the scheduling related information, and the like,which are acquired from the E-DPCCH decoder section 123 k.

In addition, as shown in FIG. 13, the MAC-e functional section 123 l isprovided with a receive processing command section 123 l 1, an HARQcontrolling section 123 l 2, and a scheduling section 123 l 3.

The receive processing command section 123 l 1 is configured to transmitthe transmission format number related information, the HARQ relatedinformation, and the scheduling related information, which are enteredfrom the E-DPCCH decoder section 123 k, to the HARQ controlling section123 l 2.

In addition, the receive processing command section 123 l 1 isconfigured to transmit, to the scheduling section 123 l 3, thescheduling related information entered from the E-DPCCH decoder 123 k.

Further, the receive processing command section 123 l 1 is configured tooutput the transmission format information corresponding to thetransmission format number entered from the E-DPCCH decoder section 123k.

The HARQ controlling section 123 l 2 is configured to determine whetheror not the receive processing of uplink user data has been successful,based on the result of CRC entered from the FEC decoder section 123 p.

Then, the HARQ controlling section 123 l 2 is configured to generate anacknowledge signal (Ack or Nack), based on the determination result, soas to transmit the generated acknowledge signal to the configuration forthe downlink of the baseband signal processing section 12.

In addition, the HARQ controlling section 123 l 2 is configured totransmit the uplink user data entered from the FEC decoder section 123 pto the radio network controller RNC, when the above determination resulthas been successful.

In addition, the HARQ controlling section 123 l 2 is configured to clearsoft decision values stored in the HARQ buffer 123 o, when the abovedetermination result has been successful.

On the other hand, the HARQ controlling section 123 l 2 is configured tostore, in the HARQ buffer 123 o, the uplink user data, when the abovedetermination result has not been successful.

In addition, the HARQ controlling section 123 l 2 is configured toforward the above determination result to the receive processing commandsection 123 l 1.

The receive processing control command section 123 l 1 is configured tonotify the E-DPDCH RAKE section 123 d and the buffer 123 m of anhardware resource that should be prepared for the following transmissiontime interval (TTI) based on the determination result, so as to performnotification for reserving the resource in the HARQ buffer 123 o.

In addition, when the uplink user data is stored in the buffer 123 m,the receive processing command section 123 l 1 is configured todesignate the HARQ buffer 123 o and the FEC decoder section 123 p toperform the FEC decode processing after adding the uplink user data,which is stored in the HARQ buffer 123 o, in a process corresponding tothe TTI and a newly received uplink user data, per TTI.

The scheduling section 123 l 3 is configured to transmit the schedulingsignals (the AGCH) and the Relative Rate Grant Channel (RGCH) via theconfiguration for the downlink.

As shown in FIG. 14, the radio network controller RNC according to thisembodiment is provided with an exchange interface 51, a Logical LinkControl (LLC) layer processing section 52, a MAC layer processingsection 53, a media signal processing section 54, a radio base stationinterface 55, and a call control section 56.

The exchange interface 51 is an interface with an exchange 1, and isconfigured to forward the downlink signals transmitted from the exchange1 to the LLC layer processing section 52, and to forward the uplinksignals transmitted from the LLC layer processing section 52 to theexchange 1.

The LLC layer processing section 52 is configured to perform an LLCsub-layer processing such as a combining processing of a header such asa sequence number or a trailer.

The LLC layer processing section 52 is also configured to transmit theuplink signals to the exchange interface 51 and to transmit the downlinksignals to the MAC layer processing section 53, after the LLC sub-layerprocessing is performed.

The MAC layer processing section 53 is configured to perform a MAC layerprocessing such as a priority control processing or a header grantingprocessing.

The MAC layer processing section 53 is also configured to transmit theuplink signals to the LLC layer processing section 52 and to transmitthe downlink signals to the radio base station interface 55 (or a mediasignal processing section 54), after the MAC layer processing isperformed.

The media signal processing section 54 is configured to perform a mediasignal processing against voice signals or real time image signals.

The media signal processing section 54 is also configured to transmitthe uplink signals to the MAC layer processing section 53 and totransmit the downlink signals to the radio base station interface 55,after the media signal processing is performed.

The radio base station interface 55 is an interface with the radio basestation Node B. The radio base station interface 55 is configured toforward the uplink signals transmitted from the radio base station NodeB to the MAC layer processing section 53 (or the media signal processingsection 54) and to forward the downlink signals transmitted from the MAClayer processing section 53 (or the media signal processing section 54)to the radio base station Node B.

The call control section 56 is configured to perform a radio resourcecontrol processing for controlling radio resources such as calladmission control processing, handover processing, and the like, achannel setup by the layer-3 signaling, and open processing, or thelike.

(Operations of Mobile Communication System According to First Embodimentof the Present Invention)

Referring to FIG. 15 and FIG. 16, operations of the mobile communicationsystem according to this embodiment of the present invention will bedescribed.

In step S101, a mobile station UE receives an Absolute Rate GrantChannel (AGCH) from a radio base station Node B. In step S102, themobile station UE increases a transmission rate in uplink to a certainvalue (1 Mbps) which is indicated by the AGCH (t=5 [TTI]).

In step S103, the mobile station UE detects receiving of the RGCH(including erroneously detected RGCH). Then, in step S104, the mobilestation UE determines whether or not each HARQ process has beenperformed once.

When the mobile station UE determines that each HARQ process has beenperformed once, in step S105, the mobile station UE changes thetransmission rate in uplink based on the received RGCH (t=9 [TTI]).

When the mobile station UE determines that each HARQ process has notbeen performed once yet, in step S106, the mobile station UE ignores thereceived RGCH. In other words, in step S106, the mobile station UE doesnot change the transmission rate in uplink based on the received RGCH(t=7 [TTI]).

(Effects of Mobile Communication System According to First Embodiment ofthe Present Invention)

The present invention can provide a transmission rate control method, amobile station and a radio base station, which can achieve a smooth datatransmission by preventing a rapid decrease of transmission rate whichis caused by the erroneous detection of the RGCH.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and the representative embodimentsshown and described herein. Accordingly, various modifications may bemade without departing from the scope of the general inventive conceptas defined by the appended claims and their equivalents.

1. A transmission rate control method for controlling a transmissionrate of data transmitted from a mobile station to a radio base stationvia an uplink, comprising: receiving, at the mobile station, an AbsoluteRate Grant Channel which indicates an absolute value of the transmissionrate from the radio base station; and ignoring, at the mobile station, aRelative Rate Grant Channel which indicates a relative value of thetransmission rate until each HARQ process has been performed once, afterreceiving the Absolute Rate Grant Channel.
 2. A mobile station forcontrolling a transmission rate of data transmitted to a radio basestation via an uplink, comprising: a receiving section configured toreceive an Absolute Rate Grant Channel which indicates an absolute valueof the transmission rate from the radio base station; and a controllingsection configured to ignore a Relative Rate Grant Channel whichindicates a relative value of the transmission rate until each HARQprocess has been performed once, after receiving the Absolute Rate GrantChannel.